1. Field of the Invention:
The present invention relates to high voltage gas insulated conducting systems and more particularly to a junction box construction of a relatively simple nature which permits a simplified construction for joining high voltage gas insulated conductors.
2. Description of the Prior Art:
A gas insulated bus system is normally provided with an inner conductor surrounded by a pressurized insulating gas such as sulfur hexafluoride, (SF-6), and a coaxial outer sheath or housing which serves as a container for the insulating gas and provides a ground plane. In constructing a gas insulated substation the bus conductors and the associated housing must be adaptable to make many bends and also provides for T-shaped connections when necessary. Generally, to keep the electric field density at a minimum, these bends or junctions are made within a spherical shaped shell which is larger in diameter than the bus housing. In the center of this shell is located a smaller sphere which provides for connections of the main conductor, and also serves to keep the field density at a low level.
U.S. Pat. No. 3,546,356 illustrates a construction of a typical prior art dual sphere joint. In this construction a continuous outer housing sphere is formed and the angular difference between the conductors to be joined is obtained by cutting or machining appropriate openings into the outer sphere. Cutting or machining the openings in the formed sphere is more expensive and difficult than forming the openings in the individual hemispheres which are later joined. The inner conductors are permanently joined to the inner sphere. This construction of joint is relatively expensive and difficult to manufacture. The inner conductors are permanently joined to the inner sphere and cannot be removed. Another problem with this construction is that the insulating spacers and supports for the inner conductors are not rigidly joined to the housing therefore more than one insulating spacer is required in close proximity to the joints.
In another prior art construction of high voltage gas insulated bus the junction box is formed from a continuous casting. This construction does not permit angular variability when necessary. In the prior art apparatus utilizing this construction the inner spherical member is supported by a separate stand-off insulator disposed within the spherical joint. A connection to the inner spherical member can thus not be made where the insulator is located.
It is desirable to have a high voltage gas insulated bus joint which can be fabricated from a few number of relatively inexpensive parts and still provide angular variability between the various conductors when necessary.